99 research outputs found
Chemical Abundances in the Secondary Star of the Black Hole Binary V4641 Sagittarii (SAX J1819.3-2525)
We report on detailed spectroscopic studies performed for the secondary star
in the black hole binary (micro-quasar) V4641 Sgr in order to examine its
surface chemical composition and to see if its surface shows any signature of
pollution by ejecta from a supernova explosion. High-resolution spectra of
V4641 Sgr observed in the quiescent state in the blue-visual region are
compared with those of the two bright well-studied B9 stars (14 Cyg and
Cap) observed with the same instrument. The effective temperature of V4641 Sgr
(10500 200 K) is estimated from the strengths of He~{\sc i} lines, while
its rotational velocity, sin (95 10 km s), is
estimated from the profile of the Mg~{\sc ii} line at 4481 \AA. We obtain
abundances of 10 elements and find definite over-abundances of N (by 0.8 dex or
more) and Na (by 0.8 dex) in V4641 Sgr. From line-by-line comparisons of eight
other elements (C, O, Mg, Al, Si, Ti, Cr, and Fe) between V4641 Sgr and the two
reference stars, we conclude that there is no apparent difference in the
abundances of these elements between V4641 Sgr and the two normal late B-type
stars, which have been reported to have solar abundances. An evolutionary model
of a massive close binary system has been constructed to explain the abundances
observed in V4641 Sgr. The model suggests that the progenitor of the black hole
forming supernova was as massive as ~ 35 Msun on the main-sequence and, after
becoming a ~ 10 Msun He star, underwent "dark" explosion which ejected only N
and Na-rich outer layer of the He star without radioactive Ni.Comment: 13 pages, 14 figures. Accepted for publication in the PASJ:
Publications of the Astronomical Society of Japa
Anatomical analysis of the left upper lobe of lung on three-dimensional images with focusing the branching pattern of the subsegmental veins
CD73-generated adenosine restricts lymphocyte migration into draining lymph nodes.
After an inflammatory stimulus, lymphocyte migration into draining lymph nodes increases dramatically to facilitate the encounter of naive T cells with Ag-loaded dendritic cells. In this study, we show that CD73 (ecto-5\u27-nucleotidase) plays an important role in regulating this process. CD73 produces adenosine from AMP and is expressed on high endothelial venules (HEV) and subsets of lymphocytes. Cd73(-/-) mice have normal sized lymphoid organs in the steady state, but approximately 1.5-fold larger draining lymph nodes and 2.5-fold increased rates of L-selectin-dependent lymphocyte migration from the blood through HEV compared with wild-type mice 24 h after LPS administration. Migration rates of cd73(+/+) and cd73(-/-) lymphocytes into lymph nodes of wild-type mice are equal, suggesting that it is CD73 on HEV that regulates lymphocyte migration into draining lymph nodes. The A(2B) receptor is a likely target of CD73-generated adenosine, because it is the only adenosine receptor expressed on the HEV-like cell line KOP2.16 and it is up-regulated by TNF-alpha. Furthermore, increased lymphocyte migration into draining lymph nodes of cd73(-/-) mice is largely normalized by pretreatment with the selective A(2B) receptor agonist BAY 60-6583. Adenosine receptor signaling to restrict lymphocyte migration across HEV may be an important mechanism to control the magnitude of an inflammatory response
The Type Ic Hypernova SN 2002ap
Photometric and spectroscopic data of the energetic Type Ic supernova (SN)
2002ap are presented, and the properties of the SN are investigated through
models of its spectral evolution and its light curve. The SN is
spectroscopically similar to the "hypernova" SN 1997ef. However, its kinetic
energy [ erg] and the mass ejected (2.5-5
) are smaller, resulting in a faster-evolving light curve. The SN
synthesized of Ni, and its peak luminosity was
similar to that of normal SNe. Brightness alone should not be used to define a
hypernova, whose defining character, namely very broad spectral features, is
the result of a high kinetic energy. The likely main-sequence mass of the
progenitor star was 20-25 , which is also lower than that of both
hypernovae SNe 1997ef and 1998bw. SN 2002ap appears to lie at the low-energy
and low-mass end of the hypernova sequence as it is known so far. Observations
of the nebular spectrum, which is expected to dominate by summer 2002, are
necessary to confirm these values.Comment: 10 pages, 4 figures, accepted for publication in ApJL, 30 April 2002
(minor changes to match the accepted version, with figures being colored
Two cases of Taeniasis Infection.
We report two cases of taeniasis caused by tapeworm infection. The first was a Japanese female, 23 years old, who had a history of eating raw meat during a visit to Thailand. She was referred to our hospital with a history of passing proglottids in feces. Taenia saginata or T. asiatica was suspected based on the proglottid morphologic features in addition to supportive information regarding her travel and dietary history. The patient was given praziquantel and the tapeworm was excreted. The second was a 35-year-old Thai male who had lived in Japan since 2000 and not left the country since that time. He had consumed beef cooked in the so-called yakiniku style and also sometimes raw, because of nostalgia for that Thai custom. The patient passed proglottids several times and then came to us. The proglottids were compatible with those of T. saginata. Praziquantel was prescribed and the tapeworm was excreted. In both cases, mitochondrial DNA analysis identified the worm species as T. saginata. Since morphological discrimination of three human-infecting Taenia species, T. saginata, T. solium, and T. asiatica, is not always possible, it is necessary to employ DNA analysis for diagnosis of taeniasis to confirm the worm species
Ultra fast quantum key distribution over a 97 km installed telecom fiber with wavelength-division multiplexing clock synchronization
We demonstrated ultra fast BB84 quantum key distribution (QKD) transmission
at 625 MHz clock rate through a 97 km field-installed fiber using practical
clock synchronization based on wavelength-division multiplexing (WDM). We
succeeded in over-one-hour stable key generation at a high sifted key rate of
2.4 kbps and a low quantum bit error rate (QBER) of 2.9%. The asymptotic secure
key rate was estimated to be 0.78-0.82 kbps from the transmission data with the
decoy method of average photon numbers 0, 0.15, and 0.4 photons/pulse.Comment: 7 pages, 3 figures, v2 : We added a comment on the significance of
our work, some minor corrections, and reference
Role of Palladin Phosphorylation by Extracellular Signal-Regulated Kinase in Cell Migration
Phosphorylation of actin-binding proteins plays a pivotal role in the remodeling of the actin cytoskeleton to regulate cell migration. Palladin is an actin-binding protein that is phosphorylated by growth factor stimulation; however, the identity of the involved protein kinases remains elusive. In this study, we report that palladin is a novel substrate of extracellular signal-regulated kinase (ERK). Suppression of ERK activation by a chemical inhibitor reduced palladin phosphorylation, and expression of active MEK alone was sufficient for phosphorylation. In addition, an in vitro kinase assay demonstrated direct palladin phosphorylation by ERK. We found that Ser77 and Ser197 are essential residues for phosphorylation. Although the phosphorylation of these residues was not required for actin cytoskeletal organization, we found that expression of non-phosphorylated palladin enhanced cell migration. Finally, we show that phosphorylation inhibits the palladin association with Abl tyrosine kinase. Taken together, our results indicate that palladin phosphorylation by ERK has an anti-migratory function, possibly by modulating interactions with molecules that regulate cell migration
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